I did some subsequent research and came up with this:

"symptomatic hypothermia pathologic reduction of body temperature as a result of decreased heat production or increased heat loss. Hypothyroidism, severe blood loss with circulatory failure, and damage to the heat-producing cells of the hypothalamus can lead to decreased heat production. Prolonged exposure to cold, overdosage of antipyretic drugs, such as aspirin, and profuse sweating (diaphoresis) are some causes of increased heat loss and resultant hypothermia.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved."

http://medical-dictionary.thefreedic...om/Hypothermia

I can't vouch for the reliability of the source, but at least is it's something.

I can see how aspirin would counteract the bodies' thickening of the blood, which may be a benefit to engaging in strenuous activities in cold weather by allowing better oxygen circulation, but I can't see how it would keep you warm, and it could be dangerous if hypothermia was an issue. This is just my opinion/speculation, I'm no expert.